Golf club shaft and golf club

ABSTRACT

A golf club is formed by winding and hardening a plurality of prepregs. High specific gravity materials having a higher specific gravity than carbon fiber are arranged on the butt side of the golf club. Arrangement of the high specific gravity materials is achieved by winding a high specific gravity material containing prepreg containing carbon fiber and a higher specific gravity material than the carbon fiber. Alternatively, the arrangement of the high specific gravity materials may be achieved by winding another high specific gravity material containing prepreg containing a glass fiber.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priorities from Japanese Patent Application No. 2011-262365 filed Nov. 30, 2011, and Japanese Patent Application No. 2011-264843 filed Dec. 2, 2011, which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a golf club shaft, more particularly to a golf club shaft made of fiber-reinforced resin. Furthermore, the present invention relates to a golf club having the same golf club shaft.

The golf club shafts are largely classified as so-called steel shafts and carbon shafts. The carbon shaft has been widely used from the viewpoints of its light-weight and a high degree of freedom of design.

The carbon shaft is formed of fiber-reinforced resin which uses carbon fiber as its major fiber. As a manufacturing method of this carbon shaft, sheet winding method has been known in the art as disclosed in Japanese Patent Application Publication No. 2010-259694. According to this manufacturing method, a sheet-like prepreg is wound around a mandrel (core bar), followed by further winding of a wrapping tape and after that, the prepreg is hardened by heating.

The heavier the front end side of a golf club on which a head is fixed, the greater the kinetic energy is produced. Thus, the golf club is able to impart a large initial velocity to a ball when a player swings, so that the flight distance of the ball can be extended. However, if only the front end side of the club is heavy, the center of gravity of the club is deflected extremely toward the front end side, so that the player may feel it difficult to swing. For the reason, when making the front end side of the shaft heavy, a grip side on the base portion is also made heavy. When the front end side and the grip side are formed to be heavy whereas an intermediate portion is formed to be light, the follow-through performance of the golf club upon swinging is improved. As described above, because the ball flight distance and the swing performance change depending on weight distribution between the front end side and the grip side, a current design of the golf club has paid more attention to weight adjustment of both the ends than before.

Although a variety of parts need to be prepared for the weight adjustment because the weight distribution varies depending on the physical capacity and taste of the player, preparation of a number of heads and shafts which differ in weight leads to increase in manufacturing cost and storage cost. Thus, for the weight adjustment, the following simple method is applied, in which, with several kinds of the heads and shafts having a different weight prepared, if the player desires to make the front end of a golf club heavy, a lead sheet is attached to the head, and if he or she desires to make the grip side heavy, a lead sheet is attached to an inside surface of the shaft on the grip side.

SUMMARY OF THE INVENTION

Consider increasing the weight of the grip side of a carbon shaft by attaching a lead sheet. The weight of the carbon shaft is lighter than a conventional metal shaft made of a metallic tube and the lead sheet having a large specific weight cannot be attached to the carbon shaft except locally. Thus, the entire grip side cannot be made heavy, so that a rotation moment changes easily depending on a grip position of a player.

An object of the present invention is to provide a golf club shaft in which a high specific gravity material is arranged on the butt side of a golf club using prepregs, and to provide a golf club using the same golf club shaft.

According to the first aspect of the present invention, there is provided a golf club shaft having a tip side and a butt side, including a plurality of prepregs being wound and hardened, wherein the plurality of prepregs comprises a high specific gravity material containing prepreg containing carbon fiber and a high specific gravity material having a higher specific gravity than the carbon fiber, wherein the high specific gravity material is arranged on the butt side of the golf club shaft.

The high specific gravity material may be metallic fiber and may be arranged in parallel to the carbon fiber in the longitudinal direction of the shaft. The elastic modulus of the carbon fiber in the high specific gravity material containing prepreg may be higher than the elastic modulus of other carbon fiber in other prepregs of the plurality of prepregs.

The high specific gravity material may be a fiber of high specific gravity material and arranged in a hoop direction of the shaft.

The high specific gravity material containing prepreg may be arranged in a range of 15 to 45% the entire length of a shaft from the butt side thereof.

When the golf club shaft is for wood club, the total weight of the high specific gravity material may be 2 to 6 g.

According to the second aspect of the present invention, there is provided a golf club including the golf club shaft according to the first aspect of the present invention mentioned above and a golf club head.

In the golf club shaft according to the first aspect of the present invention, the weight of the butt side is intensified by winding the prepregs in which the carbon fiber and the high specific gravity material are arranged. Consequently, the high specific gravity material can be arranged equally in a wide range on the butt side.

When the metallic fiber is arranged as the high specific gravity material in parallel to the carbon fiber in the high specific gravity material containing prepreg, the carbon fiber in the prepreg is preferred to have a higher elastic modulus than the carbon fiber in other prepregs, so as to prevent the elastic modulus of the shaft from lowering, because the elastic modulus of the metallic fiber is lower than the elastic modulus of the carbon fiber.

According to the third aspect of the present invention, there is provided a golf club shaft having a tip side and a butt side, including a plurality of prepregs being wound and hardened, wherein the plurality of prepregs comprises at least one high specific gravity material containing prepreg containing a high specific gravity material of glass fiber having a higher specific gravity than carbon fiber, wherein the high specific gravity material is arranged on the butt side of the golf club shaft.

The plurality of prepregs comprises the two high specific gravity material containing prepregs, the glass fiber in one of the prepregs is arranged in the longitudinal direction of the shaft, and the glass fiber in another of the prepregs is arranged in the hoop direction of the shaft.

The glass fiber may be arranged only in the hoop direction of the shaft.

The high specific gravity material containing prepreg may be arranged in a range of 15 to 45% the entire length of a shaft from the butt side thereof.

When the golf club shaft is for a wood club, the total weight of the glass fiber may be 2 to 6 g.

According to the fourth aspect of the present invention, there is provided a golf club including the golf club shaft according to the third aspect of the present invention mentioned above and a golf club head.

In the golf club shaft according to the third aspect of the present invention, the weight of the butt side is increased by winding the glass fiber containing prepreg around the butt side shaft and the high specific gravity material may be arranged equally in a wide area on the butt side.

By winding the prepreg in which the glass fiber is arranged in the hoop direction on the butt side, the crushing strength of the butt side of the shaft increases.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing prepregs which constitute a shaft according to an embodiment of a golf club shaft of the present invention.

FIG. 2A is a plan view of one of the prepregs shown in FIG. 1.

FIG. 2B is a side view of the prepreg shown in FIG. 2A.

FIG. 2C is an enlarged sectional view of the prepreg shown in FIG. 2A.

FIG. 3A is a perspective view showing a golf club.

FIG. 3B is a perspective view showing a shaft of the golf club.

FIG. 4 is a schematic view showing a prepreg constituting a shaft according to another embodiment of the golf club shaft of the present invention.

FIG. 5 is a schematic view showing a prepreg constituting a shaft according to still another embodiment of the golf club shaft of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of a golf club shaft according to the present invention will be described with reference to the accompanying drawings.

According to a manufacturing method for an embodiment of the golf club shaft of the present invention, as shown in FIG. 1, first, a mandrel 10 and prepregs 11 to 21 are prepared. The central axis line of the mandrel 10 is straight. A sectional shape perpendicular to the axis line of the mandrel 10 is circular. Although the mandrel 10 has a taper in which the tip side (head side) is small in diameter while the butt side (grip side) is large in diameter, it may have partly an identical-diameter section whose diameter is constant.

Preferably, the surface of the mandrel 10 is coated with mold release agent and after that, sheet-like prepregs 11 to 21 are wound successively.

The prepregs 11 to 21 contain fibers and matrix resin. The fibers contained in the prepregs 11 to 13 and 15 to 21 except the prepreg 14 are of carbon fiber. The fibers contained in the prepreg 14 include carbon fiber and metallic fiber.

In the prepregs 11, 14, 16, 18, 19, 20, and 21 of the present embodiment, their fibers are oriented in a straight direction, i.e., in a longitudinal direction of the shaft. In the prepregs 15, 17, the fibers are oriented in a hoop direction, i.e., in a circumferential direction of the shaft. The fiber of the prepreg 19 may be oriented in the hoop direction. The fiber orientation angle of the straight direction is 0° with respect to the shaft central axis, but the present invention is not limited to this. The fiber orientation angle of the straight direction may be in a range of 0±3°. The fiber orientation angle of the hoop direction is 90° with respect to the shaft central axis, but the present invention is not limited to this. The fiber orientation angle of the hoop direction may be in a range of 90±3°. In the prepreg 12, the fiber is oriented in +45° bias direction (a direction obliquely crossing the longitudinal direction of the shaft), and in the prepreg 13, the fiber is oriented in −45° bias direction. In the meantime, the fiber of the prepreg 12 may be oriented at −45° and the fiber of the prepreg 13 may be oriented at +45°. The fiber orientation angle of the bias direction is not limited to 45° but may be at any angle in a range of 30 to 60°.

The prepregs 12, 13, 15 to 19 have a length extending over the entire length of the shaft. (The prepregs 15, 17 may be provided only partly instead of being extended over the entire length of the shaft.) The prepregs 11, 20, 21 have a length of about 5 to 45%, particularly 8 to 30% of the entire length of the shaft, so that the prepregs 11, 20, 21 are disposed on only the tip side of the shaft. The prepreg 14 is disposed only on the butt side and its length in the longitudinal direction of the shaft is preferred to be 15 to 45% of the entire length of the shaft, more preferably to be 20 to 40%, and further preferably to be 25 to 35%.

The prepregs 15 to 19 have a width allowing themselves to be wound around the outer circumference of the mandrel 10 by only a single turn. The prepregs 11, 12, 13 have a width allowing themselves to be wound around the outer circumference of the mandrel 10 by multiple turns, for example, about 2 to 5 turns.

The thickness of the prepregs 12, 13 is preferred to be 0.125 mm or less, particularly about 0.05 to 0.1 mm. The thickness of the prepregs 15, 17 is preferred to be 0.1 mm or less, particularly about 0.02 to 0.05 mm. The thickness of the prepregs 16, 18, 19 is preferred to be 0.125 mm or less, particularly about 0.05 to 0.1 mm. The thickness (FIG. 2C) of the prepreg 14 is preferred to be 0.125 mm or less, particularly about 0.05 to 0.1 mm. The thickness of the prepregs 11, 20, 21 is preferred to be 0.125 mm or less, particularly about 0.05 to 0.1 mm.

The fiber areal weight (FAW) of the fiber of each of the prepregs 11 to 21 is preferred to be 10 to 150 g/m², particularly about 20 to 125 g/m². As a resin, epoxy resin is preferred.

The tensile elastic modulus of carbon fiber in each prepreg except the prepreg 14 is preferred to be 10 to 80 ton/mm² in the straight direction, particularly 24 to 40 ton/mm², and the tensile elastic modulus of carbon fiber in the hoop direction is preferred to be 5 to 30 ton/mm² (approximately 78.4 to 294 Gpa), particularly about 10 to 24 ton/mm². The carbon fiber in the bias direction is preferred to have a high elastic modulus of 40 ton/mm² (approximately 392 GPa) or more, for example, 40 to 46 ton/mm.

In the prepreg 14, as shown schematically in enlargement in FIG. 2C, carbon fiber bundles C and metallic fibers M as a high specific weight material are arranged in parallel in the straight direction. FIG. 2A is a plan view of the prepreg 14, FIG. 2B is a side view thereof, and FIG. 2C is a schematic view showing arrangement of the carbon fiber bundles C and the metallic fibers M.

In this prepreg 14, a small number of the metallic fibers M (preferably 1 to 5 fibers, more preferably a single fiber) is disposed between the two carbon fiber bundles C which are arranged in parallel. One carbon fiber bundle C contains 1 to 10 pieces of carbon fibers. Because generally the elastic modulus of the metallic fiber is lower than the elastic modulus of the carbon fiber, the elastic modulus of the carbon fiber in the carbon fiber bundle C is preferred to be higher than the elastic modulus of the carbon fiber of other prepregs 11 to 13, 15 to 21, for example, about 40 ton/mm² or more. As a metal of the metallic fiber M, tungsten alloy, titanium alloy, and boron are preferable. The metallic fiber is permitted to be of amorphous metal fiber. The diameter of the metallic fiber is preferred to be 10 to 500 μm, particularly about 50 to 100 μm. In the meantime, because the metallic fiber is likely to peel from matrix resin of a prepreg, in the present embodiment, the metallic fiber is sandwiched between the carbon fiber bundles so that the metallic fiber cannot peel off easily. The metallic fiber may be sandwiched by prepregs of glass fiber to prevent it from peeling off. As the carbon fiber bundle, preferably, a 1 to 24 k carbon fiber bundle, particularly preferably a 6 to 12 k carbon fiber bundle, for example, 12 k carbon fiber bundle may be used. The term “1 k” refers to a fiber bundle constituted of 1,000 pieces of the carbon fibers (approximately 6 to 9 μm). The fibers in the prepreg 14 are oriented in the straight direction, as shown in FIG. 1, but the present invention is not limited to this. The fibers in the prepreg 14 may be oriented in the hoop direction.

When winding the prepregs 11 to 21 around the mandrel 10, the prepregs 11 to 21 may be wound around one by one or it is permissible to bond one and another parts of those prepregs together and wind the bonded ones. For example, the prepregs 15, 16 may be bonded together and the prepregs 17, 18 may be bonded together. A procedure of winding the prepregs 11 to 21 around the mandrel 10 may be performed manually or by using a winding machine (called rolling machine also). After winding the prepregs 11 to 21 around the mandrel, a process of winding a wrapping tape is performed. Although not shown, the wrapping tape is wound spirally.

After the winding step, a step of hardening by heat is performed, so that matrix resin in the prepreg is hardened.

After the hardening step, the mandrel 10 is pulled out and the wrapping tape is removed so as to obtain a hardened tubular body (bare tube). Both ends of the bare tube are cut out as required and ground to obtain a golf club shaft 3 (FIG. 3B). A head 2 and a grip 4 are mounted to the golf club shaft 3 to obtain a golf club 1 (FIG. 3A).

Because in the shaft 3, the prepreg 14 arranged on only the butt side contains the metallic fiber M, the weight of the butt side of the shaft 3 is increased. A range L in which the metallic fiber M exists is preferred to be 15 to 45% of the entire length of the shaft 3 from the butt side of the shaft 3, is more preferred to be 20 to 40%, and is further preferred to be 25 to 35%. In the case of a wood type golf club shaft, the entire length of the shaft is 1,050 to 1,220 mm. In the wood type golf club shaft, the total weight of the metallic fiber is preferred to be 2 to 6 g and more preferred to be 3 to 5 g.

FIG. 4 shows an example of another lamination of the prepregs. Referring to FIG. 4, short prepregs 15A, 17A to be arranged on only the butt side are used in place of the prepregs 15, 17. The metallic fiber is used for part of fibers of the prepreg 15A like the prepreg 14 so as to increase the weight of the butt side. The prepreg 14A contains only the carbon fiber but not the metallic fiber. Other configurations are the same as FIG. 1.

Examples of laminations of the prepregs shown in FIGS. 1 and 4 are examples of the present invention, and other examples of laminations than shown in FIGS. 1 and 4 may be used. For example, in FIGS. 1 and 4, the same prepreg as the prepreg 15 (or 17) in the hoop direction may be arranged between the prepregs 18 and 19 in the straight direction. In FIGS. 1 and 4, part of the prepregs in the hoop direction, for example, the prepreg 17 may be canceled out. Furthermore, it is permissible to use 4 to 6 pieces of the bias prepregs 12, 13 in total. In an ordinary case, it is preferable to laminate 3 to 5 pieces of the prepregs constituted of fibers arranged in the straight direction, 2, 4 or 6 pieces of the prepregs constituted of fibers arranged in the bias direction, and 1 to 3 pieces of the prepregs constituted of fibers arranged in the hoop direction.

Although according to the above description, only the carbon fibers or only the carbon fibers and the metallic fibers as a high specific gravity material are contained in the prepreg, it is permissible to further mix other fibers such as glass fibers, silicon carbide fibers, alumina fibers, aromatic polyamide fibers or boron fibers.

Although according to the above description, the metallic fiber is applied as the high specific gravity material, it is permissible to contain metallic powder having a high specific gravity of 4 or higher such as tungsten, tungsten alloy, copper, copper alloy, stainless, steel, titanium, titanium alloy in the prepreg.

According to the present invention, as a high specific gravity material in the prepreg 14, the glass fiber may be used. In this case, it is also permissible to use a relatively thick prepreg in which the glass fibers are arranged in the straight direction and a relatively thin prepreg in which the glass fibers are arranged in the hoop direction.

Furthermore, a manufacturing method of a golf club shaft according to another embodiment of the present invention will be described as shown in FIG. 5. In this manufacturing method, a mandrel 10 and prepregs 51 to 61 are used. The central axis line of the mandrel 10 is straight.

Prepregs 51 to 62 contain fibers and matrix resin. The fiber for use in the prepregs 51 to 53, 56 to 62 except the prepreg 55 is carbon fiber. The fiber for use in the prepreg 55 is glass fiber.

In the present embodiment, the fibers in the prepregs 51, 54, 57, 59, 60, 61, 62 are oriented in the straight direction, i.e., the longitudinal direction of the shaft. In the prepregs 55, 56, 58, the fibers are oriented in the hoop direction, i.e., in the circumferential direction of the shaft. The fibers of the prepreg 60 may be oriented in the hoop direction. The fiber of the prepreg 52 is oriented in the +45° bias direction (obliquely crossing the longitudinal direction of the shaft) and the fiber of the prepreg 53 is oriented in the −45° bias direction. In addition, the fiber of the prepreg 52 may be oriented in the −45° bias direction and the fiber of the prepreg 53 may be oriented in the +45° direction. The bias direction is not limited to 45° but may be at any angle in a range of 30 to 60°.

The thickness of the prepregs 52, 53 is preferred to be 0.125 mm or less, particularly about 0.05 to 0.1 mm. The thickness of the prepregs 56, 58 is preferred to be 0.1 mm or less, particularly about 0.02 to 0.05 mm. The thickness of the prepregs 57, 59, 60 is preferred to be 0.125 mm or less, particularly about 0.05 to 0.1 mm. The thickness of the prepreg 54 is preferred to be 0.125 mm or less, particularly about 0.05 to 0.1 mm. The thickness of the prepregs 51, 61, 62 is preferred to be 0.125 mm or less, particularly about 0.05 to 0.1 mm. To facilitate winding of the prepreg 55, the thickness of the glass fiber containing prepreg 55 is preferred to be 0.05 mm or less, for example, about 0.01 to 0.05 mm.

The fiber areal weight (FAW) of the fiber of each of the prepregs 51 to 62 is preferred to be 10 to 150 g/m², particularly about 20 to 125 g/m². As a resin, epoxy resin is preferred.

The tensile elastic modulus of carbon fiber in each prepreg is preferred to be 10 to 80 ton/mm² in the straight direction, particularly 24 to 40 ton/mm², and the tensile elastic modulus of carbon fiber in the hoop direction is preferred to be 8 to 30 ton/mm² (approximately 78.4 to 294 Gpa), particularly about 10 to 24 ton/mm². The carbon fiber in the bias direction is preferred to have a high elastic modulus of 40 ton/mm² (approximately 392 GPa) or more, for example, 40 to 46 ton/mm.

In the glass fiber containing prepreg 15, the tensile elastic modulus of the glass fiber is preferred to be about 7 to 10 ton/mm² (approximately 68.6 to 98 GPa).

The prepregs 54, 55 may be wound together such that they overlap because their sizes are the same.

After the prepregs 51 to 62 are wound around the mandrel 10, the wrapping tape winding step is executed. Although not shown, the wrapping tape is wound spirally.

After the winding step, a step of hardening by heat is performed, so that matrix resin in the prepreg is hardened.

After the hardening step, the mandrel 10 is pulled out and the wrapping tape is removed so as to obtain a hardened tubular body (bare tube). Both the ends of the bare tube are cut out as required and ground to obtain a golf club shaft 3 (FIG. 2B) like in the above-described embodiment. The head 2 and the grip 4 are mounted to the golf club shaft 3 to obtain a golf club 1 (FIG. 2A).

Because in the shaft 3, the prepreg 55 arranged on only the butt side contains glass fiber, the weight of the butt side of the shaft 3 is increased. A range L in which the glass fiber exists is preferred to be 15 to 45% the entire length of the shaft 3 from the butt side of the shaft 3, more preferred to be 20 to 40%, and further preferred to be 25 to 35%. In the case of a wood type golf club shaft, the entire length of the shaft is 1,050 to 1,220 mm. In the wood type golf club shaft, the total weight of the glass fiber is preferred to be 2 to 6 g and more preferred to be 3 to 5 g.

Because the prepreg 55 contains glass fiber in the hoop direction, the crushing strength of the butt side of the shaft 3 is high. Thus, even if the shaft is nipped strongly with a nipping tool such as a vise upon replacement of the grip, the shaft is protected from being crushed. Although according to the above description, the prepreg 54 is a carbon fiber containing prepreg, the prepreg 54 may be a glass fiber containing prepreg in which the glass fibers are arranged in the straight direction. In this case, the thickness of the glass fiber containing prepreg is preferred to be 0.05 to 0.13 mm, particularly about 0.12 to 0.13 mm. Although in the above description, the glass fiber of the glass fiber containing prepreg 55 is oriented in the hoop direction, it may be oriented in the straight direction.

The example of the lamination of the prepregs shown in FIG. 5 is an example of the present invention and other examples of laminations than that shown in FIG. 5 may be used. For example, in FIG. 5, the same prepreg as the prepreg 56 (or 58) in the hoop direction may be arranged between the prepregs 59 and 60 in the straight direction. In FIG. 5, part of the prepregs in the hoop direction, for example, the prepreg 58 may be canceled out. Furthermore, it is permissible to use 4 to 6 pieces in total of the bias prepregs 52, 53. In an ordinary case, it is preferable to lay 3 to 5 prepregs constituted of fibers arranged in the straight direction, and 2, 4 or 6 prepregs constituted of fibers arranged in the bias direction, and 1 to 3 prepregs constituted of fibers arranged in the hoop direction.

Although according to the above description, only the carbon fibers or only the glass fibers are contained in the prepreg, it is permissible to further mix other fibers such as silicon carbide fibers, alumina fibers, aromatic polyamide fibers or boron fibers. 

What is claimed is:
 1. A golf club shaft having a tip side and a butt side, comprising: a plurality of prepregs being wound and hardened, wherein the plurality of prepregs comprises a high specific gravity material containing prepreg containing carbon fiber and a high specific gravity material having a higher specific gravity than the carbon fiber, wherein the high specific gravity material is arranged on the butt side of the golf club shaft.
 2. The golf club shaft according to claim 1, wherein the high specific gravity material is metallic fiber and arranged in parallel to the carbon fiber in the longitudinal direction of the shaft, wherein the elastic modulus of the carbon fiber in the high specific gravity material containing prepreg is higher than the elastic modulus of other carbon fiber in other prepregs of the plurality of prepregs.
 3. The golf club shaft according to claim 1, wherein the high specific gravity material is a fiber of high specific gravity material and arranged in a hoop direction of the shaft.
 4. The golf club shaft according to claim 1, wherein the high specific gravity material containing prepreg is arranged in a range of 15 to 45% the entire length of a shaft from the butt side thereof.
 5. The golf club shaft according to claim 1, wherein the golf club shaft is for a wood club, the total weight of the high specific gravity material is 2 to 6 g.
 6. A golf club comprising the golf club shaft according to claim 1 and a golf club head.
 7. A golf club shaft having a tip side and a butt side, comprising a plurality of prepregs being wound and hardened, wherein the plurality of prepregs comprises at least one high specific gravity material containing prepreg containing a high specific gravity material of glass fiber having a higher specific gravity than carbon fiber, wherein the high specific gravity material is arranged on the butt side of the golf club shaft.
 8. The golf club shaft according to claim 7, wherein the plurality of prepregs comprises the two high specific gravity material containing prepregs, the glass fiber in one of the prepregs is arranged in the longitudinal direction of the shaft, and the glass fiber in another of the prepregs is arranged in the hoop direction of the shaft.
 9. The golf club shaft according to claim 7, wherein the glass fiber is arranged only in the hoop direction of the shaft.
 10. The golf club shaft according to claim 7, wherein the high specific gravity material containing prepreg is arranged in a range of 15 to 45% the entire length of a shaft from the butt side thereof.
 11. The golf club shaft according to claim 7, wherein the golf club shaft is for wood club, the total weight of the glass fiber is 2 to 6 g.
 12. A golf club comprising the golf club shaft according to claim 7 and a golf club head. 